The concept of having a vehicle platoon moving in unison, whether in longitudinal or lateral direction, is of considerable interest when seeking to decrease traffic congestion and gas consumption, improve driver comfort and safety, and limit emissions.
In the platoon, the objective to achieve, for the longitudinal case, is each vehicle maintaining a safe and predetermined distance to the vehicle in front, called the leader. The distance would typically be dependent of velocity, since higher velocities require larger safety-distances. Arrangements are proposed through which a driver of a vehicle in such a platoon may allow the throttle and the brakes of the vehicle to be handled automatically.
With respect to lateral control of a vehicle traveling in such a platoon the objective is to follow the path of the leading vehicle and mimic its maneuvers in a stable manner. This may also be performed in an automated manner using a control algorithm. The driver may then hand over steering of the vehicle to an onboard computer.
However, much of the earlier research has been focused on utilization of vehicle platoons operating in specialized infrastructure, such as highways with magnets integrated into the path and used as road markings.
Recent developments, however, are more tended toward the implementation of platoons in unmodified roads using available sensor information and communication, such as the angle and distance to a preceding vehicle, in order to determine acceleration, braking or steering of a subject vehicle.
According to the latter concept; each vehicle will depending on its state and the state of the neighboring vehicle utilize a control strategy to follow its movements and maintain the platoon. The platoon can under these assumptions be seen as decentralized.
One previously known example is given in U.S. Pat. No. 5,781,119, which relates to a vehicle guiding system that enables a plurality of vehicles to run in a platoon. When the vehicle runs in the platoon, a front running vehicle detects its displacement from a magnetic nail, and calculates a steering amount to be corrected (i.e. control variables). The front running vehicle not only controls its own movements on the basis of the control variable data but also transmits them to a following vehicle. The following vehicle does not detect its displacement from the magnetic nail, but controls its steering amount on the basis of the received control variable data. The following vehicle includes a correcting unit for correcting the received control variable data depending upon the type of the front running vehicle and the type of the following vehicle. The following vehicle includes a transmitter for transmitting the corrected control variable data to further following vehicles. The further following vehicle simply receives the control variable data from the following vehicle, and does not calculate its own control variables. Each of the following vehicles is controlled on the basis of the corrected control variable data received from a vehicle ahead.
However, a serious issue that may arise here is error propagation throughout the platoon. In the case of the first following car being laterally displaced relative to the leader, the displacement might be amplified to the second follower, and so on.
This problem needs to be either eradicated or bounded to avoid vehicles further down the line leaving the lane.